The determination of safety and effectiveness of the new drug losigamone when used alone in the treatment of complex partial seizures. This is a randomized, double-blind parallel group trial using patients who can tolerate losigamone as the onlyantiepilepsy medication without raised seizure activity during the pre-randomization baseline period when, for four weeks, the patient will continue on the current seizure medication and count seizures. The objectives of the trial are to provide evidence of the anticonvulsant effect of losigamone as the only medication, to seek the relationship between the dosage and the tolerability, address concerns about liver and kidey clearance, to compare effects of losigamone in the bodies of males and females, and to provide additional information on the effect of losigamone on the precesses of standard antiepileptic drugs. Phase one will be the four week period of continuation of the current seizure medication and counting of seizures. The beginning of phase two is an overnight visit in the hospital to study blood levels of losigamone after a single dose. During the remainder of phase two, there will be a gradual increase of the dosage of losigamone to find the proper amount with no unacceptable side effects and no increase in seizures. During a six week phase three, the previous seizure medication will be slowly withdrawn and the dosage of losigamone will be adjusted to minimize side effects without increasing seizures. During this phase, monotherapy, using only losigamone, will be achieved. The eight week phase four will be the sole use of losigamone and a baseline seizure count. The last day will be an admission when blood and urine is collected to study how fast the body eliminates the medication. The subject will then be randomly assigned to one of two groups, one taking the same best dose and the other taking one half of the best dose. During the eight week phase five, the unknown doses will be taken and continued to the end of the phase if the number of seizures compares to the number of baseline seizures. Phase six will be final safety examinations and lab tests and eligibility to continue on an open label extension of the study will be determined.